The present invention relates to variable displacement compressors that are used in vehicle air conditioners.
Japanese Unexamined Patent Publication No. 4-303184 discloses such a compressor. The compressor according to the publication includes cylinder bores, a crank chamber, a suction chamber and a discharge chamber, which are defined in a housing. Each cylinder bore houses a piston. The compressor also has a drive shaft rotatably supported in the housing. A rotor is mounted on the drive shaft and is accommodated in the crank chamber. The crank chamber also accommodates a swash plate that slides along and tilts with respect to the axis of the drive shaft. The swash plate is coupled to the pistons. The swash plate is also coupled to the rotor by a hinge mechanism. The rotor and the hinge mechanism allow the swash plate to integrally rotate with the drive shaft. The hinge mechanism also allows the swash plate to slide along and to tilt with respect to the axis of the drive shaft between a maximum inclination position and a minimum inclination position.
The compressor further includes a displacement control valve. The control valve adjusts the pressure in the crank chamber, thereby changing the difference between the pressure in the crank chamber acting on one side of each piston and the pressure in the cylinder bores acting on the other side of the pistons. The changes in the pressure difference tilt the swash plate between the maximum inclination position and the minimum inclination position thereby changing the stroke of each piston. The displacement of the compressor is varied, accordingly.
The hinge mechanism includes a pair of support arms formed on the rotor and a pair of swing arms formed on the swash plate. An oblong guide hole is formed in each guide arm and a guide pin is press fitted in each swing arm. Each guide pin is slidably inserted in one of the guide holes. The guide holes define the path of the guide pins thereby guiding the tilting and the sliding of the swash plate on the axis of the drive shaft.
The compressor of the above publication has the following drawbacks:
The two swing arms complicate the shape of the swash plate. Accordingly, the machining of the swash plate is burdensome.
Since the pair of swing arms are arranged in a limited area on the swash plate, each swing arm is relatively small. It is therefore difficult to improve the strength and durability of the swing arms. Also, the small size of the swing arms results in a short length of the guide pins engaging with the swing arms. That is, the portion of each guide pin that is inserted into a swing arm is relatively short. It is therefore difficult to strengthen the connection between each guide pin and the associated swing arm.
The guide pins and the swing arms, which are separate parts, increase the number of parts in the hinge mechanism. This increases the number of the manufacturing steps and the manufacturing cost of the compressor.